I think it’s normal cause nursing is very comforting to them! Maybe try to change up the routine and try nap, feed, play, nap, feed, play. So they are nursing right after they wake up instead of right before they go to sleep.
I agree with @Diana somtimes my LO will suck on my nipple for comfort to help her sleep.Thats why at times I give her the pacifier so she can have that to comfort her.
My baby did the same thing I usually express milk in a bottle and she usually drinks more from that before she falls asleep.